Parkinson's disease is the most frequent movement disorder. The prevalence in people above 65 years is approximately 1% and it has a great negative effect on quality of life. The cause of Parkinson's disease (PD) is unknown and there are no disease modifying treatments available. In Parkinson's disease (PD), the cardinal motor symptoms are mainly related to the loss of dopaminergic neurons in the substantia nigra. However, neuropathologic changes are much more widespread involving the autonomic nervous system, olfactory structures, lower brainstem and cerebral cortex. Extranigral pathology is related to a broad spectrum of non-motor symptoms (NMS) that have been increasingly recognized as an important feature of PD. Gastrointestinal dysfunction, in particular constipation, affects up to 80% of PD-patients and may precede the onset of motor symptoms by years (Savica et al. 2009). Idiopathic constipation is one of the strongest risk-factors for PD (Noyce et al. 2012).
It is not known what factors initiate the pathophysiological cascade leading to neurodegeneration in PD, but an environmental factor likely plays a key role in PD pathogenesis probably against a background of genetic vulnerability (Kieburtz et al. 2013). The early involvement of the gastrointestinal tract in PD lends support to the hypothesis that this environmental factor exerts its influences primarily via the gut. However, recent studies have revealed that, changes of the complex equilibrium of the entire microbiome may be related to human disease.
Intestinal microbiota have gained a lot of attention in research in recent years and dysequilibrium of the gut microbiome has been associated with several diseases, including autism, bowel disease and cancer, rheumatoid arthritis, diabetes, and obesity. The gut microbiome in PD has not been previously investigated.
Currently there is no method available for an early diagnostics of PD. Biomarkers for PD, especially for the premotor phase, are urgently needed since future disease modifying therapies should be initiated as early as possible in the disease process to maximize their effect. Moreover, there is no disease modifying treatment available for PD.